Powered handpieces that receive and operate surgical instruments are well known in the arthroscopy field. The powered handpieces provide a mechanical drive for disposable cutting blades attached thereto. Some cutting blades have a fixed outer tube having a distal opening and an inner cutting tube received therein having a distal opening with cutting teeth. The openings together define an open window when in alignment with each other. A suction arrangement is provided to enable suction of fluid from a surgical site into the inner tube and through the handpiece to a suction device when the openings of the tubes are disposed in alignment with each other to provide a window for a flow path between the exterior of the cutting blade and the suction device.
In operation, the suction arrangement through the handpiece and blade is capable of removing large quantities of fluid from a surgical site within a short period of time. Thus, if the suction window of the cutting blade is in an open position when the cutting blade is stopped, the suction arrangement may rapidly remove fluid from the surgical site resulting in a lower pressure than that required to perform a procedure. If each and every time the handpiece is stopped the inner cutting tube stops with the window formed by the openings in a closed position, fluid management would be improved.
U.S. Pat. No. 5,733,298 to Berman, et al. discloses an endoscopic shaver blade window positioning system for a handpiece that receives an elongate shaver blade assembly. The blade assembly has a movable inner elongate member having a cutting opening at its distal end and a position indicator mounted to a movable hub at a proximal end of the inner elongate member. The position indicator rotates with the inner elongate member. The inner member is received within an elongate outer member having a distal opening. A sensor is fixed on an interior of the handpiece at the distal end thereof. In operation, the sensor detects passing of the position indicator thereby as the movable hub rotates. A window positioning system determines the position of the indicator and thus the blade assembly by determining the position of the indicator with respect to the sensor. The indicator can be a magnet, ferrous metal, bar code, reflective stripe or electrical contact that is detected by the sensor. A window control circuit controls the motor of the handpiece to stop the inner member at a predetermined position relative to the outer elongate member.
U.S. Pat. No. 5,602,449 to Krause, et al. discloses a motor controlled surgical system and method having positional control. The system includes sensors in a motor for generating electrical signals indicating a motor drive position relative to a motor drive initial position. Further, a position identifier for identifying a start-stop position of a driven surgical device is provided so that the surgical device can be stopped at a predetermined position. In other arrangements, an element secured to a rotating portion of a driven member of the surgical device has its position sensed by a sensor element secured to the handpiece that provides an electrical signal to identify when the surgical device is at a predetermined position. Thus, the surgical device may be controlled so that it always starts, ends, and/or reverses, at a known position at which an aperture at a distal end of the surgical device has a predetermined known open, closed, or partially open characteristic.
The above arrangements rely on a sensor and at least one indicator or detectable element provided with the surgical device. Disposing sensors or indicators inside of, or on disposable cutting blades or the like, as disclosed in the above patents can be of concern. Specifically, such an arrangement increases the overall cost of disposable cutting blades. Further, the cutting blades can only be utilized with a handpiece having the appropriate sensor/device for determining the position thereof.
The invention in one embodiment provides a sensor inside the shaver handpiece for detecting the position of a disposable cutting accessory so that the cutting accessory does not require a sensor or an indicator mounted thereon, while maintaining the ability to provide a selected open, partially open, or closed window for the cutting accessory of the handpiece when the accessory is stopped. Another embodiment disposes the sensor away from both the cutting accessory and the handpiece. Another embodiment enables a determination of the relative operating speed of an inner cutting element of a cutting accessory. Other embodiments optimize the cut/bite of the cutting accessory by controlling the cutting speed of the inner cutting element. Finally, another embodiment detects clogging of a suction path of the cutting accessory.
In another embodiment, the invention utilizes a pressure sensor to monitor pressure in a suction path for a handpiece having a cutting accessory attached thereto. The cutting accessory is defined by a movable cutting element and a fixed cutting element having openings or apertures at distal ends thereof. A window is defined by the movable and fixed cutting elements. As the movable cutting element rotates or reciprocates, the window closes and opens to periodically define a suction path. A pressure difference occurs in the suction path each time the window opens/closes. Thus, a resulting pressure pattern has minimum and maximum pressure values occurring at a frequency that corresponds to the frequency of rotation or reciprocation of the inner cutting element. When the cutting window defined by a movable cutting element and a fixed cutting element is open, an increase in measured pressure occurs, and when the cutting window is closed, a pressure decrease in the suction tube occurs. Thus, the pressure sensor determines the velocity of movement for the inner cutting element relative to the outer cutting element.
Besides tracking the velocity of the inner cutting element, the pressure sensor can determine the location of the opening of the inner cutting element relative to the opening of the outer cutting element. Measured pressure values enable a control system to track the location of the inner cutting element and to adjust the location of the window to a desired final position when the inner cutting element is stopped. For example, the inner cutting element can be stopped with its opening at a closed position relative to the opening of the outer cutting element. This arrangement enables fluid management for a cutting accessory located at a surgical site.
In one embodiment, a pseudo smart-handpiece is provided with a pressure sensor in the suction flow path of the handpiece. A controller in the handpiece can adjust the speed of rotation of the inner cutting element depending on the pressure sensed by the pressure sensor and measured joint pressure to obtain a predetermined desired average fluid flow rate along the suction path. By adjusting speed of the inner cutting element due to suction pressure and joint pressure, the bite/cut of the cutting element can be maximized.
Further, a change of pressure, such as a sudden decrease in pressure may be measured to indicate a clogging of the cutting window. In such instance, the suction pressure would remain low as no fluid is drawn through the window.
In one embodiment a fluid flow sensor is provided in a suction path for a handpiece having a cutting accessory attached thereto as discussed above. As the movable cutting element rotates or reciprocates, the window opens and closes so that a measurable flow difference occurs periodically. Thus a fluid flow pattern results having maximum and minimum flow values occurring at a frequency that corresponds to the frequency of rotation or reciprocation of the inner cutting window.
Besides tracking the velocity of the inner cutting element, the flow sensor determines the location of the opening of the inner cutting element relative to the fixed outer cutting element. Thus, the inner cutting element can be stopped at a desired final position, for instance with the window in a closed position. Further, sensing essentially no fluid flow while the inner cutting element is rotating or reciprocating indicates clogging of the cutting window.
In another embodiment of the invention, a pseudo smart-handpiece is provided with a flow sensor in the suction flow path of the handpiece. A controller can adjust the speed of rotation of the inner cutting element to maintain the fluid flow through the suction flow path at a predetermined average flow rate taken by averaging the high and low fluid flow values or integrating the flow value measured over a time period to obtain a predetermined optimal overall average fluid flow rate for the liquid, and in many instances cut tissue, passing through the suction bore. This flow control arrangement maximizes the bite/cut of the cutting accessory.
Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement, and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.